Relaxed sampling for service latency, as 0 disables it.

[aricart]

Fixed new staticcheck errors

[coveralls]

Pull Request Test Coverage Report for Build 305

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 89.094%

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Totals
Change from base Build 299:	0.0%
Covered Lines:	1062
Relevant Lines:	1192

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💛 - Coveralls

[kozlovic]

Not sure this is correct. We do the same check in the server when parsing local config: https://github.com/nats-io/nats-server/blob/master/server/opts.go#L1932.
When updating an account, if the jwt.Export.Latency (a *jwt.ServiceLatency object) is not nil, then server tries to track for latency and will fail if sampling is < 1 or > 100.
So not sure what is the right thing to do here... @derekcollison wdyt?

[aricart]

we had an informal discussion where we said that 0 would disable the check thus allowing the configuration to have the subject etc, but be turned off easily. Perhaps this is not correct but nsc does allow the zero.

[derekcollison]

I think its correct, we should remove it all together to disable IMO.